This invention relates to a nonaqueous secondary battery which has a high discharge potential, a long life, and excellent safety and which can be produced with improved productivity.
JP-A-61-7577 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) discloses a positive electrode having a protective layer comprising a substance having electron conductivity combined with ionic conductivity (e.g., lithium ion conductivity), giving an oxide of tungsten, molybdenum or vanadium as a preferred example of the substance having electron and ion conductivity. However, the compounds enumerated have not achieved sufficient effects in preventing internal short-circuits.
JP-A-4-28173 discloses providing a polymer film which selectively transmits an alkali metal ion on the surface of a negative electrode made of an alkali metal or an alkali metal alloy countering to a positive electrode. However, use of such a porous polymer film is fraught with the problem that the battery capacity may be greatly reduced.
Accordingly, an object of the present invention is to improve productivity in the production of a nonaqueous secondary battery having a high discharge voltage, satisfactory charge and discharge cycle characteristics, and excellent safety.
The object of the present invention has been accomplished by the following nonaqueous secondary batteries.
(1) A nonaqueous secondary battery comprising a positive electrode and a negative electrode both containing a material capable of reversibly intercalating and deintercalating lithium, and a nonaqueous electrolyte containing a lithium salt, wherein at least one of the negative electrode and positive electrode has at least one protective layer containing at least one inorganic oxide selected from the group consisting of alumina, silicon dioxide and zirconia.
(2) A nonaqueous secondary battery comprising a positive electrode and a negative electrode both containing a material capable of reversibly intercalating and deintercalating lithium, and a nonaqueous electrolyte containing a lithium salt, wherein at least one of the negative electrode and positive electrode has at least one protective layer containing organic fine particles.
(3) A nonaqueous secondary battery comprising a positive electrode containing a material capable of reversibly intercalating and deintercalating lithium, a negative electrode containing at least one oxide selected from the group consisting of a metal or semimetal oxide belonging to the groups 13 to 15 of the Periodic Table which is capable of reversibly intercalating and deintercalating lithium, a nonaqueous electrolyte containing a lithium salt, and a separator, wherein at least one of the negative electrode and positive electrode has at least one protective layer.